Disclosed herein is a vehicle seat, and particularly, a vehicle seat with improved impact energy absorption efficiency upon a rear-end collision or the like.
Generally, when a so-called rear-end collision occurs, for example, when a vehicle is rear-ended or upon a significant collision occurring when a vehicle travels rearward, a seated occupant suddenly moves rearward due to an inertial force, and the occupant's upper body inclines rearward.
Various techniques have been proposed that are characterized by such a configuration that a side frame composing a seat back frame is bent when the sudden rearward movement of the occupant causes a rear load to be applied to the seat back frame so that the impact load applied to the occupant upon the rearward movement is mitigated (for example, International Patent Application Publication No. WO 2012/077764 (“the '764 Document”)).
A seat back frame of a vehicle seat disclosed in the '764 Document includes side frames positioned on right and left sides, and a lower frame that connects lower parts of these side frames.
This lower frame is formed in a shape that is widened in a vertical direction as it extends from a center portion thereof toward right and left end portions thereof, and flexible narrow portions are formed in upper parts of the right and left end portions.
These narrow portions horizontally extend from both ends on the outer sides in the right-left direction of the right and left end portions toward the inner side of the seat, incline upward as they come toward the inner side of the seat, and are formed in long shapes extended toward the upper edges of the right and left end portions.
The configuration is such that, when an impact load is applied to the seat, for example, upon a rear-end collision of the vehicle or the like, these narrow portions are deformed preferentially, and the deformation is transmitted from the narrow portions toward upper edges of the right and left end portions.
In this way, by limiting deformed portions of the seat back frame, propagation of impact energy throughout the entirety of the seat back frame can be prevented, and impact energy can be absorbed stably.
In the vehicle seat as disclosed in the '764 Document, however, deformation is transmitted in one direction from the narrow portions toward the upper edges of the right and left end portions when an impact load is applied, and it is impossible to diffuse the direction in which warping deformation is transmitted. Therefore, a vehicle seat has been desired wherein impact absorbability is further improved, by diffusing the transmission direction of warping deformation of the seat.
Besides, the vehicle seat as disclosed in the '764 Document includes narrow portions that are preferentially subjected to warping deformation when an impact load is applied. Therefore, a vehicle seat in which the rigidity of the seat back frame in normal use is further improved has been desired.
Further, the narrow portions of the vehicle seat disclosed in the '764 Document are included in the right and left end portions of the lower frame, and are extend in long shapes from both ends on outer sides in the right-left direction toward the inner sides in the right-left direction. Therefore, a vehicle seat has been desired that is capable of sufficiently absorbing impact even when lengths of the narrow portions in the extension direction are decreased in the case where areas where the narrow portions are formed are limited.